Created an Assertion for StatusCodeShouldBeSuccess

src/Alba.Testing/Acceptance/asserting_against_status_code.cs

@@ -69,5 +69,53 @@ public async Task happily_blows_up_on_an_unexpected_500()
             ex.Message.ShouldContain("Expected status code 200, but was 500");
             ex.Message.ShouldContain("the error text");
         }
+
+        [Fact]
+        public async Task using_scenario_with_StatusCodeShouldBeSuccess_happy_path()
+        {
+            router.Handlers["/one"] = c =>
+            {
+                c.Response.StatusCode = 204;
+                c.Response.ContentType("text/plain");
+                c.Response.Write("Some text");
+
+                return Task.CompletedTask;
+            };
+
+            var ex = await Exception<ScenarioAssertionException>.ShouldBeThrownBy(() =>
+            {
+                return host.Scenario(x =>
+                {
+                    x.Get.Url("/one");
+                    x.StatusCodeShouldBeSuccess();
+                });
+            });
+
+        }
+
+        [Fact]
+        public async Task using_scenario_with_StatusCodeShouldBeSuccess_sad_path()
+        {
+            router.Handlers["/one"] = c =>
+            {
+                c.Response.StatusCode = 500;
+                c.Response.ContentType("text/plain");
+                c.Response.Write("Some text");
+
+                return Task.CompletedTask;
+            };
+
+            var ex = await Exception<ScenarioAssertionException>.ShouldBeThrownBy(() =>
+            {
+                return host.Scenario(x =>
+                {
+                    x.Get.Url("/one");
+                    x.StatusCodeShouldBeSuccess();
+                });
+            });
+
+            ex.Message.ShouldContain("Expected status code 200, but was 500");
+        }
+
     }
 }

src/Alba.Testing/Assertions/StatusCodeSuccessAssertionTests.cs

@@ -0,0 +1,69 @@
+using Alba.Assertions;
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Xunit;
+
+namespace Alba.Testing.Assertions
+{
+    public class StatusCodeSuccessAssertionTests
+    {
+        [Theory]
+        [ClassData(typeof(SuccessStatusCodes))]
+        public void HappyPath(int statusCode)
+        {
+            var assertion = new StatusCodeSuccessAssertion();
+
+            AssertionRunner.Run(assertion, _ => _.StatusCode(statusCode))
+                .AssertAll();
+        }
+
+        [Theory]
+        [ClassData(typeof(FailureStatusCodes))]
+        public void SadPath(int statusCode)
+        {
+            var assertion = new StatusCodeSuccessAssertion();
+
+            AssertionRunner.Run(assertion, _ => _.StatusCode(statusCode))
+                .SingleMessageShouldBe($"Expected a status code between 200 and 299, but was {statusCode}");
+        }
+    }
+
+
+
+}
+
+public class SuccessStatusCodes : IEnumerable<object[]>
+{
+    public IEnumerator<object[]> GetEnumerator()
+    {
+        foreach (var code in Enumerable.Range(200, 99))
+        {
+            yield return new object[] { code };
+        }
+    }
+
+    IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
+
+}
+
+public class FailureStatusCodes : IEnumerable<object[]>
+{
+    public IEnumerator<object[]> GetEnumerator()
+    {
+        foreach (var code in Enumerable.Range(100, 99))
+        {
+            yield return new object[] { code };
+        }
+        foreach (var code in Enumerable.Range(300, 200))
+        {
+            yield return new object[] { code };
+        }
+    }
+
+    IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
+
+}

src/Alba/Assertions/StatusCodeSuccessAssertion.cs

@@ -0,0 +1,22 @@
+using Microsoft.AspNetCore.Http;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Alba.Assertions
+{
+    public class StatusCodeSuccessAssertion : IScenarioAssertion
+    {
+        public void Assert(Scenario scenario, HttpContext context, ScenarioAssertionException ex)
+        {
+            var statusCode = context.Response.StatusCode;
+            if(statusCode < 200 || statusCode >= 300)
+            {
+                ex.Add($"Expected a status code between 200 and 299, but was {statusCode}");
+                ex.ReadBody(context);
+            }
+        }
+    }
+}

src/Alba/ScenarioExpectationsExtensions.cs

@@ -50,6 +50,16 @@ public static Scenario StatusCodeShouldBeOk(this Scenario scenario)
             return scenario.StatusCodeShouldBe(HttpStatusCode.OK);
         }
 
+        /// <summary>
+        /// Assert tha the Http Status Code is between 200 and 299
+        /// </summary>
+        /// <param name="scenario"></param>
+        /// <returns></returns>
+        public static Scenario StatusCodeShouldBeSuccess(this Scenario scenario)
+        {
+            return scenario.AssertThat(new StatusCodeSuccessAssertion());
+        }
+
         /// <summary>
         /// Assert that the content-type header value of the Http response
         /// matches the expected value